Many different overhead industrial light fixtures exist to serve needs such as factory and warehouse illumination and the like, and a number of advances have been made over the years. Among significant advances in industrial light fixtures are the fixtures disclosed in U.S. Pat. Nos. 6,601,975 (Overhead Industrial Light Fixture With Two-Piece Housing); 6,394,869 (Method for Manufacture of Overhead Industrial Light Fixture); and 6,467,927 (Overhead Industrial Light Fixture With Mounted Reflector), all of Ruud Lighting, Inc. Such fixtures provide significant advantages, including compactness, simplicity of manufacture, ease of installation and service, pleasing appearance, and other advantages set forth in the disclosures.
Despite these and other such advances in the field there remains a need for further improvement in industrial light fixtures, preferably without compromising the advantages previously provided including those related to ease of manufacture, storage, shipment, installation, etc.
One concern of particular significance is that overhead industrial light fixtures of the prior art are predisposed to a variety of problems associated with overheating. Overheating can damage power-related components (e.g., capacitors) which ultimately compromises the longevity of the light fixture and its components. Among the overheating problems with certain devices of the prior art is a problem of inadequate heat dissipation away from power-related components, such as ballasts, lamps and lamp sockets.
Another problem is that certain structures of the prior art may not be particularly well-adapted to suppress and/or contain any combustion that might occur. In certain cases, the nature of the ballast (including manufacturing defects or minimal defects that may occur from handling or the like) or improper electrical characteristics or conditions can lead to ballast failures and shorts which in turn lead to combustion of materials (e.g., organic insulation materials). As can be seen, the goals of achieving cooling and suppressing oxidation in an industrial light fixture tend to be at odds with each other. Accomplishing one of these critical goals tends to lead to loss of the other. The benefits realized in being able to accomplish these two goals in one fixture would be significant.
For one thing, facilitating cooling of the industrial light fixture tends to keep the components cool thereby enhancing the life of the components and the entire fixture and preserving overall quality. And, substantially reducing the inflow and outflow of combustion-supporting air in critical portions of an industrial light fixture would tend to suppress and limit any combustion which might occur, and thus reduce dangers typically associated with product failures. If these critical advantages could be combined in an industrial lighting fixture, the resulting fixture would have improved quality, endurance and longevity.
Ballasts, the electrical components required to start and maintain operation of lighting fixtures, are prone to overheating. During regular operation, the ballast produces considerable heat and often receives heat from the lamp it serves. When overheating of the ballast occurs, it can cause breakdown of the ballast core. It would, therefore, be particularly important in the design of an overhead industrial light fixture to achieve maximum heat dissipation from the ballast and to thermally separate the ballast from the heat of the lamp, while at the same time facilitating containment of any combustion which might occur upon ballast failure.
While the concern of overheating has in some cases been addressed by use of baffles and other insulating features, such approaches increase manufacturing costs and comprise the desirable goal of compactness and ease of service. Plastic ballast enclosures may be used to insulate the ballast; however, such enclosures are contrary to heat removal and can exacerbate problems. In many other cases, this concern has led to inclusion of thermal protection devices to break circuits upon any overheating. However, in the case of thermal protection devices, under certain conditions, such devices may fail to perform properly thereby allowing a lighting fixture to overheat and possibly lead to combustion. Such thermal protection devices also add cost.
Another possible approach to dealing with certain of the above problems and shortcomings is use of a housing with one or more external power-related components, such as the ballast. However, this approach complicates installation, increases cost, makes achieving a pleasing appearance difficult at best, and is directly contrary to the goal of compactness.
The subject matter described herein is directed to one approach to overcoming the aforementioned problems and shortcomings.